1. Field of the Invention
The subject invention is directed to an apparatus used for separating individual mail pieces from a stack and correctly orienting those mail pieces for further processing and, more particularly, to an apparatus comprised of multiple conveyor subsystems oriented in series where the conveyors are individually controlled.
2. Description of the Prior Art
The process of separating one mail piece from a stack is referred to as singulation. Singulating mail pieces is an essential step in processing the mail pieces to their ultimate destination. Special problems arise in the singulation process when handling mail pieces, called "flats", which fall within the following size ranges: height between three and fifteen inches, length between four and a quarter inches and fifteen inches, thickness between seven one thousandths of an inch and one inch, and weight up to four pounds. Such mail flats may include magazines, folded newspapers, stiff documents such as vehicle license plates, as well as large envelopes.
Many prior art feeders use vacuum forces to accomplish singulation. In operation, a vacuum head applies suction to one side of a mail flat and separates it from the other flats by picking it up and transporting it. The vacuum pickup heads in these feeders are virtually useless in handling mail pieces such as magazines and folded newspapers because the vacuum forces can only apply vacuum suction to one, or a few, of the multiplicity of sheets of the magazine or newspaper, leaving the rest of the sheets to dangle freely from the pickup head. In addition, present day feeders generally operate on the principle that mechanization is provided only to separate the first document from a stack of documents, with little or no provision being made for further attempts at separation. Thus, if a double feed occurs, the documents enter the system and eventually must be removed before further processing can be performed.
U.S. Pat. No. 4,328,962 to Akers discloses an envelope feeder apparatus for use with mail sorting machines which includes a plurality of conveyor subsystems. Each conveyor subsystem has a pair of friction belts. Each of the belts has a plurality of holes which allow a suction pressure to be exerted therethrough for aiding in holding a leading envelope against the friction belts. The Akers device is not designed to singulate a pile of randomly sized and oriented mail pieces; rather, envelopes, all of which are the same size, must be correctly placed in an angularly oriented magazine before being transported through the device. Hence, the conveyor subsystems of the Akers device are merely designed to move envelopes through a plurality of different stations.
U.S. Pat. No. 4,697,689 to Carrell discloses an article manipulation system for singulating a heap of irregular mail pieces and orienting the mail pieces with the address in the upward direction. The singulating subsystem comprises a plurality of cylindrical rollers, each having a high friction surface for engagement with mail pieces and each being independently driven by a motor. The rollers are separated from one another and are in a generally horizontal plane. A set of low friction slats are positioned between adjacent rollers at a level slightly below the topmost surface of the rollers. The rollers and the slats are in close enough proximity to one another such that mail pieces are prevented from sliding therebetween. The singulation process is enhanced through coordinated operation of the motors. When the rollers are moved together, the parcels are conveyed across the singulation subsystem. When the rollers moved individually, they separate parcels from the heap. In the Carrell device, the cooperative action of the rollers does not always produce singulation, i.e., isolation of a single parcel; therefore, Carrell has found it necessary to provide a robotic arm between the singulating subsystem and the orienting subsystem which pushes and lifts parcels to separate them.